Serial4j post-nullary connection handling enhancements

[pavly-gerges]

This PR adds some enhancements for the C++ and the Java APIs after introducing device nullary connections detection mechanisms:

• C++ SerialPort: define default values to protect against memory access violations and memory segmentation.
• Java TerminalDevice#openPort(): updated the Java SerialPort structure SerialPort#ioFlag from the FilePermissions API for the native SerialPort to operate correctly.
• C++ TerminalDevice::closePort(): updated the native SerialPort structure SerialPort::portOpened, SerialPort::ioFlag, and SerialPort::fd for the JVM SerialPort to operate correctly.
• C++ TerminalDevice::fetchSerialPorts(AddressBuffer *): implemented anti-buffer-overflow mechanisms for the dynamic path allocator using a compatible buffer size with the required path of the device in query.